DESCRIPTION: (Applicant's Description) Despite the very high incidence of prostate cancer in the U.S., the etiology of this disease remains elusive. Although dietary factors are thought to play a role, no definitive relationships have yet been established. This project will use a prospective design to investigate several blood and urinary biomarkers of prostate cancer risk that are directly or indirectly related to diet, and which show sufficiently low intra-to-inter-individual variation to be practical for study. Blood biomarkers will include prediagnostic levels of fatty acids, insulin-like growth factors, and androgenic hormones as potential risk factors, and levels of selenium, carotenoids, and vitamin E as potential protective factors. Urinary biomarkers will include a major F2-isoprostane as a risk factor, and several phytoestrogens as protective factors. Blood and urine specimens will be collected from 18,535 male Oahu members of the Multi- ethnic Cohort, on whom extensive demographic, dietary, and other exposure information was collected by self-administered questionnaire in 1993-1996. For a biomarker calibration study, a second collection will be made on a subset of 150 men 3-12 months later. The men represent three ethnic groups: Japanese, Caucasians, and Native Hawaiians. Blood specimens will be separated into plasma, serum, red cell and buffy coat components and stored in 0.5 cc cryotubes in liquid N2 freezers. Urines will be stored in 2.0 cc aliquots at -80C. Incident cases of prostate cancer in the subcohort will be identified through the rapid reporting system of the Hawaii Tumor Registry, as well as by direct contact with the subjects. The bioassays will be carried out on a projected 273 cases and 546 controls (matched to the cases on age, ethnicity, both month and time of day of sample collection, and fasting status) in a nested case-control design. PSA levels will also be used to further characterize cases and define controls. Data analysis will determine overall measures of risk for the several biomarkers, and will examine ethnic variations as well as interactions between biomarkers and other risk factors. This study should help identify biomarkers of prostate cancer risk that may be useful for future interventions.